I shoot my 17HMR’s quite a bit to almost 200 and like them for small varmint hunting, sage rats and PD’s and the like. Very accurate and no recoil. You can practice positions and trigger control, etc. But they are nearly useless in the wind at any distance. They are good practice, but I don't see them as a substitute for a .223/5.56.
Besides small varmints, what I think they excel at is helping a new shooter build confidence and competence before moving up to a .223 class cartridge. We have a rimfire silhouette range at my club with numerous small metal targets. Some are not easy to knock over with the 17HMR for my grands. So it requires them to hit a spot on the target, often the head. Real good practice for them. 50-100 rounds there then off to the 100, 200 & 300 ranges with the .223.
The kapow of a center fire is also good practice for them. That’s how I use my 17HMR’s anyway. So I say make sure you have both.